An Alkylated Indacenodithieno[3,2-b]thiophene-Based Nonfullerene Acceptor with High Crystallinity Exhibiting Single Junction Solar Cell Efficiencies Greater than 13% with Low Voltage Losses

Zhuping Fei; Flurin D Eisner; Xuechen Jiao; Mohammed Azzouzi; Jason A Röhr; Yang Han; Munazza Shahid; Anthony S R Chesman; Christopher D Easton; Christopher R McNeill; Thomas D Anthopoulos; Jenny Nelson; Martin Heeney

doi:10.1002/adma.201705209

An Alkylated Indacenodithieno[3,2-b]thiophene-Based Nonfullerene Acceptor with High Crystallinity Exhibiting Single Junction Solar Cell Efficiencies Greater than 13% with Low Voltage Losses

Adv Mater. 2018 Feb;30(8). doi: 10.1002/adma.201705209. Epub 2018 Jan 9.

Affiliations

¹ Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London, SW7 2AZ, UK.
² Department of Physics and Centre for Plastic Electronics, Imperial College London, London, SW7 2AZ, UK.
³ Department of Materials Science and Engineering, Monash University, Victoria, 3800, Australia.
⁴ CSIRO Manufacturing, Ian Wark Laboratories, Clayton, Victoria, 3168, Australia.
⁵ Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.

PMID: 29315933
DOI: 10.1002/adma.201705209

Abstract

A new synthetic route, to prepare an alkylated indacenodithieno[3,2-b]thiophene-based nonfullerene acceptor (C8-ITIC), is reported. Compared to the reported ITIC with phenylalkyl side chains, the new acceptor C8-ITIC exhibits a reduction in the optical band gap, higher absorptivity, and an increased propensity to crystallize. Accordingly, blends with the donor polymer PBDB-T exhibit a power conversion efficiency (PCE) up to 12.4%. Further improvements in efficiency are found upon backbone fluorination of the donor polymer to afford the novel material PFBDB-T. The resulting blend with C8-ITIC shows an impressive PCE up to 13.2% as a result of the higher open-circuit voltage. Electroluminescence studies demonstrate that backbone fluorination reduces the energy loss of the blends, with PFBDB-T/C8-ITIC-based cells exhibiting a small energy loss of 0.6 eV combined with a high J_SC of 19.6 mA cm^-2 .

Keywords: conjugated polymers; crystal engineering; nonfullerene acceptors; organic solar cells.